The term 'Ancient Theatre' refers to the earliest form of theatre, which dates back to the 6th century BC. One example of an Ancient Theatre is the ODEON, which is a 5-letter word. The ODEON was a type of theatre that was used in Ancient Greece and Rome for musical performances, poetry readings, and other forms of entertainment. It was typically built in a semi-circular shape with tiers of seating, and it was often used for political gatherings and religious ceremonies.